1. Field of the Invention
This invention relates to separation and more particularly to an apparatus and a method for separating solids from a liquid such as separating solids settled or suspended within a liquid.
2. Background of the Invention
The prior art has known various devices for separating solids from a liquid. A particular problem exists for separating large volumes of solids from large volumes of liquid. This particular problem exists in the separation of large volumes of solids from sewage treatment plants, water retention ponds, channel dredging or similar problems of separating large volumes of solids.
Municipal waste or the like is conveyed to a local sewage treatment plant in which the raw sewage is treated in various sedimentation processes after which the primary sludge is further treated in an aeration tank or basin for biological degradation thereof. Although most sewage treatment plants incorporate bar screens and grit chambers for removing entrained granular material from the sewage to be treated, in practice a considerable amount of granular material reaches the aeration basin where such granular material accumulates.
The primary function of the aeration basin or aeration tank is to supply a steady stream of oxygen through the sewage contained in the aeration basin. Such oxygen enhances the ability of bacteria comprising the bio-mass within the aeration basin to feed upon and thereby degrade and decompose the sewage. However, as the level of granular material accumulates within the aeration basin, the effective depth of the basin decreases. Therefore, the flow path of the air through the sewage aeration basin becomes shortened as the granular material accumulating within the aeration basin increases. This decrease in the distance travelled by the air through the sewage to be treated reduces the efficiency with which the sewage may be treated by such oxygen and this results in the requirement for more air for longer periods of time to compensate for the decrease in efficiency of the system as the granular material displaces the capacity of the aeration tank.
Another problem encountered with the accumulation of granular material within the aeration basin is that occasionally such accumulated solids will break loose and will travel downstream from the aeration basin and actually plug air diffusers and the like thereby reducing the efficiency of the aeration process. Furthermore, if such granular material is carried completely over into an adjacent treatment tank, plugging of percolation ponds or drain fields may occur.
Above all, due to the accumulation of sand or similar granular material at the base of the aeration basin, the overall cost of operating the sewage treatment plant will increase because not only will the capacity of the aeration basin be reduced thereby reducing the overall effectiveness of the plant, but also because sewage plants are subject to peak flows at certain hours of the day. These flow surges are normally buffered by the correct sizing of the aeration chamber or basin. However, when the aeration basin includes an accumulation of sand and other solids, this buffering effect is impaired and solids will pass through the aeration tank without being properly treated with the oxygen stream.
When sand or the like accumulates within the base of an aeration basin, not only are greater loading requirements placed upon aeration equipment and ancillary pumping gear, but the reduced efficiency of the aeration tank requires greater amounts of chlorination to meet required regulations and all these associated inefficiencies result in a greatly increased cost when operating the sewage plant.
In the past, when sand or the like has accumulated in the bottom of an aeration tank, two alternative recourses have been available to the sewage plant operator. Firstly, the sewage may be diverted if practical to an alternative treatment plant while the sand is removed from the aeration chamber manually or secondly, the sewage contained within the aeration tank must be removed therefrom into transportation tanks for removal to an alternative plant. In either case, it is necessary to shut down the sewage plant while such removal of granular material from the aeration tank is carried out. Additionally, the removal of sand or similar granular material from the bottom of an aeration basin is a time consuming and unpleasant occupation, and results in removal of the beneficial biomass as well.
In my prior inventions, I disclosed an apparatus and a method for removing granular material from an aeration basin while such aeration basin is still filled with sewage, without interrupting the normal operation of the sewage plant. The apparatus provided a collector disposed within the aeration basin for collecting the granular material from the base of the basin and for pumping the granular material to a first separator where the granular material settles to the bottom of the first separator and is conveyed by a conveyor for separating the granular material from the waste material and for pumping waste water and sewage back from the first separator to the aeration basin.
U.S. Pat. No. 4,707,277 to Mims discloses an apparatus for removing granular material from an aeration basin of a sewage plant. The apparatus includes a collector for collecting the granular material from the aeration basin. A first pump includes an input and an output port with the input port being in fluid tight communication with the collector for pumping and removing the granular material out of the aeration basin together with a portion of the sewage and waste water contained within the basin. A float is disposed on the surface of the sewage within the aeration basin, the float adjustably supporting the collector relative to the granular material to be removed. A buoyant conduit is connected to the output port of the first pump such that the buoyant conduit conducts the removed granular material, sewage, wastewater and bio-mass from the float away from the aeration basin. A mobile reservoir includes an inlet and an outlet, the inlet being connected to the buoyant conduit such that the granular material, sewage and wastewater removed from the aeration basin flows into the reservoir and the granular material settles towards the outlet. A separator having a first and a second opening is disposed with the first opening adjacent to and in fluid communication with the outlet of the reservoir. The separator extends angularly relative to the reservoir such that as the waste water and entrained granular material are conveyed away from the first opening of the separator towards the second opening, the waste water and bio-mass drains back towards the first opening and the granular material is separated from the waste water and is conveyed towards the second opening of the separator for discharge therefrom.
U.S. Pat. No. 4,818,419 to Mims discloses a filter device. A collector is positioned proximate the clogged filter medium for collecting the clogged filter medium together with a portion of the water contained within a tank housing the clogged granular filter medium. An input of a first pump is connected in fluid tight communication with the collector. A conduit is connected in fluid tight communication with an output port of the first pump. The conduit is connected to a reservoir. The clogged granular filter medium and the portion of water is pumped by the first pump from the tank of the granular filter device such that a slurry of clogged granular filter medium flows from the granular filter device through the collector, first pump and conduit towards the reservoir such that during the transit through the collector, first pump and conduit the clogged granular filter medium is agitated causing an intergranular frictional action among the clogged granular filter medium thereby loosening the clogging material from the granular filter medium to form a suspension of loosened clogging material and entrained granular filter medium. The granular filter medium is separated from the suspension of loosened clogging material by conveying granular filter medium angularly relative to the reservoir thereby permitting the suspension of loosened clogging material and granular filter medium to be conveyed away from the first opening of the separator towards a second opening of the separator, so that the suspension of loosened clogging material drains back towards the first opening thereby separating the granular filter medium from the suspension of loosened clogging material to form a cleaned granular filter medium. The cleaned granular filter medium is collected from the second opening of the separator and transported back to the granular filter device.
U.S. Pat. No. 4,818,420 to Mims discloses a liquid filtering and backwashing apparatus comprising a filter tank having a first outlet valve and a filter cell disposed within the filter tank. The filter cell includes a conduit and an outer member with the outer member spaced apart relative the conduit with a filtering medium positioned between the conduit and the outer member. A plurality of openings in the outer member enable fluid communication between the liquid to be filtered in the filter tank and the filtering medium. The conduit is provided with a plurality of slits to enable fluid communication between the filtering medium and interior of the conduit while retaining the filtering medium external the conduit. A backwash holding tank in fluid communication with the conduit collects the filtered liquid. The backwash holding tank includes a second outlet valve for the filtered liquid to drain. When the filter cell becomes clogged with the filter clogging material the first outlet valve is opened, the second outlet valve is closed, and the backwash holding tank is provided with compressed gas through an inlet valve forcing filtered liquid back into the filter cell and filter tank thereby backwashing the filter cell and filter tank.
U.S. Pat. No. 4,957,622 to Mims discloses an apparatus and method for removing sediment which has settled on the bottom of a pond comprising a frame and a hydrostatic chamber. The hydrostatic chamber includes an aperture to receive the sediment and water proximate the bottom of the pond. A gate controls the size of the opening of the aperture formed in the hydrostatic chamber thereby regulating the ratio of sediment to water entering the hydrostatic chamber. An underwater motive means moves the apparatus along the bottom of the pond causing a wiper to extend into the sediment for scraping, loosening, wiping and plowing the sediment from the bottom of the pond and for directing the bottom sediment toward the aperture upon movement of the frame by the motive means. A vent is used to vent the hydrostatic chamber while a pump is in fluid communication with the hydrostatic chamber to create a pressure differential thereby forcing into the hydrostatic chamber the sediment and fluid proximate the aperture. This sediment and fluid is pumped out for disposal away from the pond.
U.S. Pat. No. 5,013,457 to Mims discloses a liquid filtering and backwashing apparatus comprising a pressurized filter tank having a first outlet valve and a filter cell disposed within the filter tank. The filter cell includes a conduit and an outer member with the outer member spaced apart relative to the conduit with a filtering medium positioned between the conduit and the outer member. A plurality of openings in the outer member enable fluid communication between the liquid to be filtered in the filter tank and the filtering medium. The conduit is provided with a plurality of slits to enable the pressure in the tank to force fluid communication between the filtering medium and interior of the conduit while retaining the filtering medium external the conduit. Means are provided to vary the size of the slits to adjust for differing pressures or filtering requirements. A backwash holding tank in fluid communication with the conduit collects the filtered liquid. The backwash holding tank includes a second outlet valve for the filtered liquid to drain. When the filter cell becomes clogged with the filter clogging material the first outlet valve is opened, the second outlet valve is closed, and the backwash holding tank is provided with compressed gas through an inlet valve forcing filtered liquid back into the filter cell and filter tank thereby backwashing the filter cell and filter tank.
U.S. Pat. No. 5,167,841 to Mims discloses an apparatus and method for removing granular material and debris from a basin of a body of water. The apparatus comprises a first pump having an input port for collecting granular material, debris and water from of the basin. A conduit conducts the removed granular material, debris and water from the basin to a mobile reservoir. An Archimedean screw conveyor extends angularly relative to the mobile reservoir for conveying the granular material, debris and water away from the mobile reservoir and for separating the granular material and debris from the water. A second pump discharges the water from the mobile reservoir back into the basin.
U.S. Pat. No. 5,244,308 to Mims discloses an apparatus and method for an improved mobile apparatus for removing contaminants from a site containing granular material with the contaminants being affixed thereto. The mobile apparatus comprises a processor which extracts the granular material containing the contaminants from the site. The processor containing a liquid agent separates the contaminants from the granular material and creates a slurry comprising the granular material, the liquid agent and the contaminants. A conduit conducts the slurry from the processor to a mobile reservoir. A separator extending angularly relative to the mobile reservoir conveys the granular material, the liquid agent and the contaminants away from the mobile reservoir and separates the granular material from the liquid agent containing the contaminants.
It is an object of the present invention to improve upon my prior inventions and to provide an improved apparatus and method for separating a solid from a liquid having an enhanced performance.
Another object of this invention is to provide an improved apparatus and method for separating a solid from a liquid incorporating a cyclone separator for concentrating the solids within the liquid prior to separating the solids from liquid.
Another object of this invention is to provide an improved apparatus and method for separating a solid from a liquid incorporating a second cyclone separator for concentrating the remaining solids within the liquid after the initial separation process.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed as being merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention with in the scope of the invention. Accordingly other objects in a full understanding of the invention may be had by referring to the summary of the invention, the detailed description describing the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.